Dynamometers have long been used to determine the force, torque, and power produced by rotating machines and other rotating devices and systems of various types for testing, calibration, and similar purposes. Most of these kinds of dynamometers are equipped with some way to measure the operating torque and rotational speed or angular velocity of the unit or system to be tested or evaluated. Power is then calculated from these measurements. Either torque or speed can be maintained constant during operation of the dynamometer while the other parameter of the machine, device, or system being tested is measured. Typically, a dynamometer will include an absorber/driver unit that is rotatably coupled to the machine or system to be tested so that this unit can rotate at whatever speed is required for testing and has structure designed to develop a braking torque. Torque measurement can be made in a variety of ways, including through the use of torque transducers that provide an electrical signal proportional to torque. Speed measurements can also be made similarly through speed sensors or transducers that provide electrical signals proportional to speed. These electrical signals can be transmitted to appropriate processors for analysis.
Some currently available dynamometers use electric motor/generators as absorber/driver units. Either an alternating current (AC) motor or a direct current (DC) motor can operate as a generator that is driven by the machine or device being tested. These dynamometers are equipped with control elements, usually a variable frequency drive for an AC motor or a DC drive for a DC motor. If the control elements are regenerative, power can be transferred from the machine being tested to an appropriate destination.
There are, in addition, various types of dynamometer systems, depending on the type of load applied to the machine or system being tested. For example, a brake type of dynamometer applies a variable load and measures the machine's ability to move or hold speed compared to an applied braking torque and calculates power output from the applied braking torque. An inertia type of dynamometer provides a fixed inertial load with a known mass, usually a heavy drum, and calculates the power required to accelerate that load from recorded speed and acceleration rate of the machine or device to be tested. Torque can be calculated from recorded speed and acceleration rate. These dynamometer systems have real world limitations, however. The use of a fixed inertial load, for example, requires all load tests to be conducted under acceleration conditions. In situations in which a machine or system must also be able to perform under fixed speed conditions, the use of a fixed inertial load cannot determine machine or system performance. Testing a machine, device, or system at a speed that is variably set by a variable load is not possible with the systems described.
A direct motor type of dynamometer, which has two opposing motors and is typically used to test one of the motors, may effectively test the motor, but cannot effectively test other structures, such as, for example, vehicle wheels, load on a wheel due to brakes, and the like. In a vehicle with one or more drive wheels powered by a motor, the ability to test such drive wheels, as well as any associated structures that constitute a load on the wheel, can provide essential performance information. This capability is not provided by currently available dynamometers.
A range of dynamic load test systems has been described in the prior art. In U.S. Pat. No. 3,898,875, for example, Knoop et al describe a system for testing an electric motor that is rigidly mounted in a stationary platform and fixedly coupled through torque and speed transducers to a load motor that is designed to test dynamic characteristics of the motor under test over a short time interval. Linear deceleration is followed by linear acceleration during the testing interval, which is short enough to prevent substantial heating of the test motor. U.S. Pat. No. 4,807,467 to Kugler describes a testing system useful for drive units, including complete motor vehicles, internal combustion engines, transmissions, brake systems, and the like, that provides a realistic simulation of flywheel masses and torque variations. This system, which employs a hydrostatic motor and supporting hydraulic apparatus, is stated to allow precise regulation and adjustment of a desired load and torque more accurately than electric motor equipment used for the same purpose. U.S. Patent Application Publication No. US2011/0077892 to Emamai et al describes a test platform for testing electric motors under specific load conditions to which the motor will be subjected in real-world applications that is designed to enable motor purchasers to connect a motor accurately to the test platform and evaluate the motor prior to purchase. A load emulator also permits components other than motors, such as motor drive systems, transmission mechanisms, including harmonic drives, planetary gear boxes, and the like, and rotary internal combustion engines to be tested. This system additionally enables the testing to be conducted remotely over a network.
The patent art has also proposed dynamometers for testing aircraft components. U.S. Pat. No. 4,753,110 to Burchett et al describes a dynamometer useful for measuring forces, brake torque, and rolling resistance of tires and brakes of aircraft, as well as other vehicles, in which a runway is simulated by the surface of a rotatable drum, and a tire wheel and brake assembly is adjustably mounted on a transducer head connected to a mounting plate that can be adjusted to change the camber and yaw angle of the tire, while a traveling carriage connected to the mounting plate may be advanced toward the drum by a drum ram. In U.S. Pat. No. 5,945,598, Enright describes a dynamometer for testing aircraft brakes that realistically simulates brake and landing gear vibration dynamics, particularly the vibrational coupling between brakes and gear walk, in which a hydraulic pitch motion inducer forces a wheel tire and brake assembly against a road wheel or drum. The load is designed to simulate aircraft weight for an individual wheel and brake assembly. Neither of these patents suggests testing a powered aircraft wheel or wheel connected structures or functions under realistic acceleration and deceleration conditions and fixed and/or variable speeds or loads.
None of the prior art described above suggests an integrated active resistance dynamometer testing apparatus with the capability for testing a wheel or a powered wheel system under simulated realistic load and speed conditions in which either and/or both load and speed can be flexibly varied or fixed to measure desired selected parameters relating to wheel function or operation. The prior art, moreover, also fails to suggest such a testing apparatus that can accommodate and perform such tests on wheels, wheels powered by drivers or motors, brakes or other loads on wheels, tires, antiskid and/or traction control functions, or other wheel-connected structures and functions under simulated realistic conditions. A need for a system and method to conduct such testing under simulated realistic conditions exists.